Panel comprising a polymeric composite layer and a reinforcement layer

ABSTRACT

A panel comprises a polymeric composite layer and at least a reinforcement layer for reinforcing the polymeric composite layer at least in the plane of the panel. The reinforcement layer is made of a material which is different from that of the polymeric composite layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Section 371 National Stage Application ofInternational Application PCT/EP2011/060991 filed Jun. 30, 2011 andpublished as WO 2012/001091 A1 in English.

BACKGROUND

The discussion below is merely provided for general backgroundinformation and is not intended to be used as an aid in determining thescope of the claimed subject matter.

Aspects of the present invention relate to a panel, in particular afloor panel which comprises a polymeric composite layer.

A panel having a layer of a polymeric composite is known from WO2008/122668. In this case the polymeric composite is WPC, which is acomposite of polymeric material and a natural fiber for example from anywood source. Due to the presence of polymers the dimensions of the knownpanels depend on temperature more strongly than for example wooden floorboards or panels mainly made of wood-based material, which limits theapplicability of panels including a WPC layer.

SUMMARY

This Summary and the Abstract herein are provided to introduce aselection of concepts in a simplified form that are further describedbelow in the Detailed Description. This Summary and the Abstract are notintended to identify key features or essential features of the claimedsubject matter, nor are they intended to be used as an aid indetermining the scope of the claimed subject matter. The claimed subjectmatter is not limited to implementations that solve any or alldisadvantages noted in the Background.

An aspect of the present invention is to provide a panel including apolymeric composite layer which is applicable in changing ambientconditions.

For this purpose the panel comprises a reinforcement layer forreinforcing the polymeric composite layer at least in the plane of thepanel, which reinforcement layer is made of a material which isdifferent from that of the polymeric composite layer. The reinforcementlayer may also reinforce the polymeric composite layer in a directionextending transversely to the plane of the panel.

An advantage of the panel is that deformation of the polymeric compositelayer in the plane of the panel is minimized. In other words, thesensitivity of the dimensions of the panel to ambient conditions isminimized. This means that the panel can be applied at locations whereambient conditions change, for example in case of floor panels that areconnected to each other to form a flooring on a floor having a floorheating system. Furthermore, in case of floor panels that are mutuallyconnected to form a flooring, the expansion clearance between the walland an adjacent floor panel can be minimized. In practice, thereinforcement layer is thinner than the polymeric composite layer, forexample less than 0.4 mm but a greater thickness is possible. It isnoted that the reinforcement layer may be a sheet or plate; the layermay be self-supporting and/or made of one piece.

The polymeric composite may be a mixture of one or more polymers andnon-polymeric or partly polymeric material. Examples of non-polymeric orpartly polymeric materials are chalk and carpet waste, jute, styrenebutadiene (latex), but a lot of alternative materials are conceivable.The polymeric composite may further contain a coupling agent to improvethe material cohesion. Alternative additives are elastomers or materialshaving a high absorption capacity of fillers. This may also improvecharacteristics like UV resistance, humidity resistance and bendingstrength. The fillers may be fibers, powders or the like. In general,the polymeric composite layer may be a composite of a polymer and anon-polymer composite substance. The composite substance may be naturalor non-natural fibers, particles or the like. In a practical embodimentthe polymeric composite layer is a WPC layer made of wood plasticcomposite (WPC) and the reinforcement layer is a non-WPC reinforcementlayer.

In one embodiment the reinforcement layer is incorporated within thepolymeric composite layer since this creates an efficient reinforcementof the polymeric composite layer. In terms of manufacturing such anembodiment the reinforcement layer can easily be integrated in a knownpressing process for manufacturing a polymeric composite panel such thatthe reinforcement layer is embedded within the polymeric compositelayer. Such a process is described in WO 2008/122668.

The reinforcement layer may have an open structure. The advantage isthat upon pressing melted granulate layers together whereas thereinforcement layer is sandwiched between the layers a strong bondbetween the melted granulate layers at open areas of the open structurecan be achieved. As a result the reinforcement layer is fully integratedin the polymeric composite layer without significantly weakening thepanel at the reinforcement layer in a direction perpendicular to theplane of the panel. Thus, the resulting polymeric composite layer iscontinuous through open areas of the open structure, i.e. in a directionperpendicular to the plane of the panel.

The reinforcement layer may comprise longitudinal filaments andtransversal filaments extending in transverse direction with respect tothe longitudinal filaments. The filaments may be orientedperpendicularly with respect to each other but this is not necessary.The mutual distance of at least one of the longitudinal filaments andtransversal filaments may vary within the reinforcement layer, whichprovides the opportunity to create a stronger reinforcement atpredefined areas of the panel. For example, the mutual distance may varybetween 1-5 filaments per cm. It is advantageous when the mutualdistance is adapted to the size of the granulate of which the polymericcomposite layer is made; in particular if the granulate is not entirelymelted it can still pass through the reinforcement layer upon pressing.The filaments may be made of glass fiber, or fibers of polyester hightenacity, polyester textile, cellulose, aramid, PEN, Nomex or othermaterials that are dimensionally insensitive to changing ambientconditions such as temperature changes.

It is noted that the filaments may be fixed to each other by a fixingmechanism, for example glue. Both the filaments and the fixing mechanismwill be selected such that they are compatible with polymeric compositeand in one embodiment form a strong bond therewith. Additionally,binders may be added to the polymeric composite and/or to thereinforcement layers, such as acrylate, ethylenvinyl acetate,polyurethane, polyvinyl alcohol, polyvinyl acetate, polyvinylchloride,styrene butadiene or the like.

The panel may comprise at least another reinforcement layer, which, inone embodiment, is located at a distance from the reinforcement layer. Aplurality of reinforcement layers is possible, as well. Thereinforcement layers may be located within the polymeric compositelayer.

The panel may be a floor panel, ceiling panel, wall panel, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the invention will hereafter be elucidated with reference tovery schematic drawings showing an embodiment of the invention by way ofexample.

FIG. 1 is an enlarged sectional view of an embodiment of a panel.

FIG. 2 is a series of very schematic top views of different types ofreinforcement layers, being applicable in the panel according to FIG. 1.

FIG. 3 is a series of perspective views of different types ofreinforcement layers, being applicable in the panel according to FIG. 1.

FIG. 4 is a very schematic view of an apparatus for manufacturing apanel of FIG. 1.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT

FIG. 1 shows a cross-sectional view of an embodiment of a floor panel 1.The floor panel 1 includes a WPC layer 2 made of wood plastic composite(WPC) granulate and a reinforcement layer 3. The reinforcement layer 3is thinner than the WPC layer 2 and is intended to minimize dimensionalchanges of the WPC layer 2 in the plane of the panel 1. In thisembodiment the reinforcement layer 3 is incorporated within the WPClayer 2 such that portions of the WPC layer 2 extend at both sides ofthe reinforcement layer 3. For stability reasons it is preferred thatthe thicknesses of these portions of the WPC layer 2 are substantiallyequal. It is noted that instead of WPC an alternative polymericcomposite may be applied.

Furthermore, the floor panel 1 according to FIG. 1 includes a toplaminate on the WPC layer 2. In this example, the top laminate is a highpressure laminate construction comprising at least a printed decorativelayer 4 and an impregnated protective overlay 5 pressed together withheat and pressure to become one single layer due to the impregnationmaterial which, in one embodiment, is a resin such as melamine resin. Ina further embodiment, the melamine resin is mixed with urea formaldehydeto obtain advantageous properties such as minimized shrinkage andreduced cloudiness. In one embodiment, the overlay paper 5 is a highabrasive overlay which can have aluminium oxide or other abrasiveresistant hard particles embedded in the surface of the paper. It isnoted that a different layer type can be provided on the WPC layer, forexample a polymeric film having a decoration pattern, which is printedon the film. The polymeric film may be melted to the WPC layer.

The top laminate or top layer as described above consists of one or morepaper layers, but also one or more wood veneer layers, vulcanizedcellulose layers or other layers suitable as top layer are conceivable.

The design and overall upper layers can be textured such as embossed inregister with the design of the printed decorative layer in order toeven better imitate natural material, such as stone, brick, ceramic,wood, marble or the like.

Preferably but not necessarily a backing layer 6 is provided below theWPC layer 2 and is fixed to the underside of the WPC layer 2. Thebacking layer 6 can be used as a balancing layer and it may also havemoisture resisting properties. Furthermore, a paper layer 7 may beprovided between the WPC layer and the top laminate.

At least on two opposite sides of the floor panel 1 and in oneembodiment on all sides are formed coupling mechanisms 8 to coupleadjacent panels 1 together. In one embodiment, the coupling mechanisms 8also include a mechanical locking system to lock the adjacent floorpanels 1 not only in a direction perpendicular to the surface of thepanels, but also in a direction parallel to the surface andperpendicular to the respective side of the floor panel 1. However theinvention is not limited thereto at all. Although FIG. 1 shows a tongueand a groove as coupling mechanisms 8, all coupling systems, includingthe use of adhesives is encompassed by the invention.

In an advantageous embodiment the reinforcement layer 3 has an openstructure, since this allows the portions of the WPC layer 2 at bothsides of the reinforcement layer 3 to contact each other duringmanufacturing, hence creating an integral structure of the WPC layer 2and the reinforcement layer 3. FIG. 2 shows several examples ofreinforcement layers 3 including an open structure. The reinforcementlayers 3 as shown comprise parallel longitudinal filaments 9 andparallel transversal filaments 10 which extend in a transverse directionwith respect to the longitudinal filaments 9. The filaments 9, 10 areoriented such that they envelope open areas 11. Although thelongitudinal filaments 9 and transversal filaments 10 in the embodimentsare perpendicularly orientated with respect to each other this is notnecessary. FIG. 2 also shows that the reinforcement layers 3 may vary inrespect of mutual distances of the filaments 9, 10 in differentdirections, even within specific portions of the reinforcement layer 3,and in filament dimensions.

FIG. 3 shows examples of different reinforcement layers 3 in perspectiveview. The longitudinal filaments 9 and transversal filaments 10 may layon each other and may be mutually attached at intersections of thefilaments 9, 10. Alternatively, the longitudinal filaments each compriseparallel filaments 9′, 9″ which are attached to each other along thefilaments 9′, 9″ and interrupted by the transversal filaments 10 whichare sandwiched between the parallel filaments 9′, 9″ at intersections ofthe filaments 9′, 9″ and the transversal filaments 10. Furthermore, thefilaments 9, 10 may be laminated to a fabric 11, for example a nonwoven, as illustrated in the lower drawing of FIG. 3.

FIG. 4 shows an apparatus 12 for manufacturing laminate sheets S whichmay include a plurality of panels 1 (see FIG. 1) which are cut from thesheets S and are finished in a manner well known in the prior art.

The apparatus 12 includes a first granulate supply 13 including amechanism 14 which is adapted to supply a first layer of granulate 15 ona supporting conveyor belt 16. The apparatus 12 further includes asecond granulate supply 17 including a mechanism 18 which is adapted tosupply a second layer of granulate 19.

Between the first granulate supply 13 and the second granulate supply 17the reinforcement layer 3 is supplied by unwinding it from a supplyroller. The second layer of granulate 19 is supplied on top of thereinforcement layer 3.

The granulate is made from wood/plastic composite which is a materialknown in the prior art. It may include from about 30 wt % to about 95 wt% of at least one polymeric material and from about 5 wt % to about 80wt % of at least one natural fiber or flour by weight of the WPC layer.Alternatively, the polymeric composite includes fibers, particles, flouror the like, that comprises one or more polymers itself, to whichpossibly one or more polymeric materials are added. The polymericmaterial can be one or more polymers having a polyolefin group, such aspolyethylene. Other exemplary polymers include polypropylene, polyvinylchloride, copolymer of PVC, and also other suitable thermoplastics. Thepolymer material to be processed can be in powder, liquid, cubed,pelletized form and/or any other form. The polymeric material can bevirgin, recycled or a mixture of both. Additionally, the polymericmaterial may be provided with natural or non-natural additives, and/or acoupling agent to improve the material cohesion. The polymeric materialcan be incorporated with a blowing agent to make a cellular foamstructure core.

The natural fibers or flour have a specific moisture content, dependingon the WPC-board specifications and requirements. The natural fibers canbe from any wood source, cellulose source, other natural sources, or anycombination thereof. Generally, any natural fiber can be used, which isfrom trees, plants, parts thereof and the like. The specific selectionof a particular type of wood and/or wood fibers can have an influence onthe properties of the final panel. The fibers of an exotic hard woodtype could for example be substantially thicker and/or longer thannormal fir wood. The bending stiffness will be higher if the WPC layeris made with longer fibers. Synthetic fibers may also be used to enhancemechanical properties such as flexural and tensile modules of theproduct. The natural fiber or flour can be virgin, recycled or a mixtureof both. Furthermore the natural fibers or flour can be incorporatedwith a foaming agent to make a cellular foam structure core.

The mechanisms 14, 18 may include a system provided by Schilling-KnobelGmbH, as is described in WO 99/26773, which is incorporated herein byreference thereto, including a hopper which is resting on a meteringroller which picks up the material to be scattered on the conveyor belt16. Other means are of course conceivable.

The lower conveyor belts 16 has a greater length than a second, upperconveyor belt 20 which is positioned at a distance from the first andsecond granulate supply 13, 17.

The upper and lower conveyor belt 16, 20 run over a certain lengthparallel to each other and include various zones. The first zone in thedirection of conveyance of the conveyor belts 16, 20 is a heating zone21. In this zone, the WPC granulate is heated to such temperature thatthe granulate melts to a sufficient extent in order to weaken to a masswhich can be shaped into a solid continuous sheet. The heatingtemperature depends on the polymer used in the WPC granulate and can forexample be between 180° C. and 250° C. In this exemplary embodiment, theheating zone 21 is divided in a first heating zone 21A and a secondheating zone 21B with nip rollers 22 in between. These nip rollers 22are positioned below the transport part of the lower conveyer belt 16and above the transport part of the upper conveyor 20 to effect a firstpressing action on the layers 15, 19 of melted granulate. A second setof nip rollers 23 consisting of two pairs of upper and lower nip rollerseffects a final pressing action on the layers 15, 19 of melted granulateand determines the final thickness of the sheet to be formed.

As described hereinbefore the reinforcement layer 3, in one embodiment,has an open structure such that the first and second layers of themelted granulate 15, 19 are pressed to each other through the open areas11 of the reinforcement layer 3. This avoids any weak bond between thelayers 15, 19 due to the addition of the reinforcement layer 3.

The last zone within the conveyor belts 16, 20 is an annealing zone 24by which the sheet layers 15, 19 are cooled and brought in the finalform. The conveyor belts 16, 20 are formed by two reinforced, thermallystable coated belts, for example from glass plus Teflon®. The back sidesof the belts are in contact with heating platens in the heating zones21A, 21B and with cooling platens in the annealing zone 24. The platensin the upper conveyor belt 20 are movable in vertical direction, whilethe platens in the lower conveyor belt 16 are rigidly mounted. Themovability of the platens with the upper conveyor 20 is to create a gapaccording to the required thickness of the sheet to be formed. Inprinciple, the heating and cooling platens do no exert pressure on thegranulate layers 15, 19 and only the calibrating nip rollers 22, 23 areadapted to exert a pressure on the melted granulate layers 15, 19 todetermine the thickness thereof.

As illustrated in FIG. 4 there is supplied a layer of paper or otherabsorbing material 6, 7 to the lower side of the first layer 15 andupper side of the second layer 19 of granulate 3 in order to be meltedthereto, i.e. to be attached thereto through the melted plastic from thegranulate. The paper layers 6, 7 are supplied by unwinding them fromsupply rollers. The paper layers 6, 7 are interposed between the firstgranulate layer 15 and the lower conveyor belt 16 and between the secondgranulate layer 19 and the upper conveyor belt 20, respectively, so thatthey also assist in preventing the granulate layers 15, 19 from stickingto the conveyor belts 16, 20. The conveying speed of the paper layers 6,7 and the reinforcement layer 3 will be configured to that of theconveyor belts 16, 20 so that they are matching, but it is also possiblethat they are not positively supplied, but are pulled away by thefriction between the paper and reinforcement layers and the granulatelayers 15, 19 and the conveyor belts 16, 20.

Instead of paper layer 7 it is possible to supply a polymeric sheet, forexample polypropylene, PVC, polyester or the like, to the melted layerof granulate of the WPC layer. The polymeric film melts and as a resultafter pressing, the resulting panel obtains a smooth surface at the sidewhere the polymeric sheet is provided and melted. This is advantageousif the WPC layer has a coarse surface due to inhomogeneous mixing of thepolymer and a composite substance. Additionally, the melted polymericlayer on the WPC layer may also improve the stability and stiffness ofthe resulting panel and further improve the adherence of still anotherpolymeric film thereon which is provided at a later stage such that itdoes not fully melt. This further polymeric film may be provided with adecoration pattern. It is also possible to provide a melted polymericlayer or film at the back side of the WPC layer, which may function as abalancing layer.

At a position downstream of the upper conveyor belt 20 there is arrangeda cutting mechanism 25 to cut the continuous sheet web into separatesheets S which are then collected for further processing so as to formthe floor panel 1 as shown in FIG. 1.

An alternative method of manufacturing the panels is one in which a toplaminate and optionally also a backing layer is fixed directly to theWPC layer simultaneously with the formation of the WPC layer includingthe reinforcement layer 3. This means that the (paper) layers 6 and 7are then formed by the materials for forming the top laminate and thebacking layer which are directly fixed to the WPC layers by adherencethereto. The top laminate should then be of such structure that it canbe supplied in rollers and can be fixed directly to the second WPClayer. The top laminate or top layer may consist of paper layers, butalso one or more wood veneer layers or vulcanized cellulose layers areconceivable according to the present invention as long as they withstandthe heat during pressing. In a further alternative embodiment, the toplaminate can be left out and the decor can be printed directly on theWPC material. As an alternative or additionally, the raw WPC materialcan be embossed and/or chafed/sanded in a particulate pattern to imitatenatural materials such as wood or stone.

From the foregoing, it will be clear that aspects of the inventionprovide a panel of which the dimensions are stable despite of varyingambient conditions.

The invention is not limited to the embodiment shown in the drawings anddescribed hereinbefore, which may be varied in different manners withinthe scope of the claims and the technical equivalents. For example, thereinforcement layer may be fixed to an outer side of the WPC layerinstead of being incorporated therein.

1. A panel, comprising a polymeric composite layer and at least areinforcement layer for reinforcing the polymeric composite layer atleast in the plane of the panel, the reinforcement layer being made of amaterial which is different from that of the polymeric composite layer.2. The panel according to claim 1, wherein the polymeric composite layeris a WPC layer made of wood plastic composite (WPC) and thereinforcement layer is a non-WPC reinforcement layer.
 3. The panelaccording to claim 1, wherein the reinforcement layer is incorporatedwithin the polymeric composite layer.
 4. The panel according to claim 1,wherein the reinforcement layer has an open structure.
 5. The panelaccording to claim 4, wherein the polymeric composite layer iscontinuous through open areas of the open structure.
 6. The panelaccording to claim 1, wherein the reinforcement layer comprises a fiberweb.
 7. The panel according to claim 1, wherein the reinforcement layercomprises longitudinal filaments and transversal filaments extending intransverse direction with respect to the longitudinal filaments.
 8. Thepanel according to claim 7, wherein the mutual distance of at least oneof the longitudinal filaments and transversal filaments vary within thereinforcement layer.
 9. The panel according to claim 1, wherein thethickness of portions of the WPC layer at both sides of thereinforcement layer is substantially equal.
 10. The panel according toclaim 1, wherein the reinforcement layer is a sheet or plate.
 11. Thepanel according to claim 1, wherein the reinforcement layer is aself-supporting layer.
 12. The panel according to claim 1, wherein thereinforcement layer is made of one piece.
 13. The panel according toclaim 1, wherein the panel comprises at least another reinforcementlayer.
 14. The panel according to claim 1, wherein the reinforcementlayer is thinner than the polymeric composite layer.
 15. The panelaccording to claim 1, wherein the polymeric composite layer contains atleast 30% polymer.